52 LABORATORY BACTERIOLOGY 
EXERCISE XIII 
THE CLASSIFICATION OF BACTERIA AND THE 
EXAMINATION OF CULTURES 
80. The term “ bacteria” is a general and popular one used 
to designate a large group of microscopic plants, the Schzzo- 
mycetes. "These organisms, which are widely distributed in 
nature, have been classified into a certain few families and 
genera, most of which have a large number of species. Many 
of these species have been described, but there are many which 
have not. In classifying the bacteria, the genera are based on 
morphologic characters, while, as a rule, the species are deter- 
mined by means of their biochemic, physiologic, or pathogenic 
properties. Several systems of classification have been pro- 
posed, but the one which seems to be the most satisfactory is 
by Migula. This classification utilizes the morphology to such 
good advantage that its adoption seems desirable. It requires, 
however, some serious changes in the accustomed nomen- 
clature ; but this is true of any logical system. The restoration 
of the genus Bacterium and the assigning to it of all non- 
motile, rod-shaped organisms change the genus of some of 
our most common pathogenic bacteria from Bacillus to Bac- 
terium. The most conspicuous of these are the bacilli of 
tuberculosis, glanders, and diphtheria, all of which are placed 
in Migula’s classification in the genus Bacterium. 
81. Work for this exercise. Read the references on the 
morphology and classification of bacteria. 
Reéxamine all the cultures previously made and make care- 
ful notes of any changes that have occurred in their appearance. 
Measure the gas in the fermentation tubes and determine 
the ratio of CO, toH. Sat 9 ge 
Discard all the cultures made and clén the tubes and Petri 
dishes [§ 3, (/)]. 
